A short official summary of the options. Pay-as-you-go credits never expire and are the simplest way to start. Prepaid packages give the lowest price per token and stay valid for twelve months. Monthly subscriptions suit steady production workloads. Every request is billed by input and output tokens, and the cheapest available tokens on your account are used first. If a charge ever looks wrong, open a thread in Billing with the order number and the time window, and we will review it.